50,000 cardiac valve replacements (CVR) are performed each year in the United States. Despite decreased surgical mortality, neurologic, neuro- ophthalmologic, and neuropsychologic morbidity remains at least twice that associated with aortocoronary bypass. Interventions that decrease the incidence of postoperative cognitive dysfunction are urgently needed. This randomized, placebo-controlled trial will consist of the administration of nimodipine pre- and postoperatively to patients undergoing CVR to determine: 1. Whether nimodipine, compared to placebo, alters the combined prevalence of new post-cardiac valve replacement neurologic, neuro-ophthalmologic, and neuropsychologic deficits 5-7 days postoperatively. 2. Whether nimodipine, compared to placebo, alters the length of post- cardiac valve replacement hospital stay. 3. Whether nimodipine, compared to placebo, alters the combined prevalence of residual post-cardiac valve replacement neurologic, neuro- ophthalmologic, and neuropsychologic deficits 6 months postoperatively. 4.Whether nimodipine, compared to placebo, alters intraoperative global CBF and cerebral metabolic indices (e.g. jugular venous oxygen saturation). 5. The relationship between cerebral blood flow and cerebral metabolism and neurologic, neuro-ophthalmologic, and neuropsychologic outcome. 6. Whether demographic factors (such as advanced age) and CPB factors (such as hypotension and prolonged CPB duration) are associated with a higher prevalence of new post-cardiac valve replacement neurologic, neuro- ophthalmologic, and neuropsychologic deficits. The Program Project of which this project is a component has combined the multidisciplinary resources necessary to establish the effects of nimodipine on neurologic outcome and to correlate the pharmacologic effects of nimodipine on cerebral blood flow and metabolism with subsequent outcome. If the information obtained from this study results in a decrease in the prevalence of neurologic deficits following these common operations, the social and financial benefit to society would be great.